Channel 4 director of television and content Kevin Lygo today stole a march on the broadcaster's critics by outlining a "creative overhaul" that could cost it both ratings and revenue.

As Channel 4 celebrates its 25th anniversary later this year, Mr Lygo and his head of programmes, Julian Bellamy, announced a bold plan to clear the broadcaster's decks of almost all its popular 9pm reality and factual entertainment programmes.

Celebrity Big Brother will be a notable sacrifice, with Channel 4 dropping the programme in 2008 following the controversy of racist abuse on this year's series.

Shows such as Brat Camp and You Are What You Eat will disappear to make way for new programme ideas, meaning the only show that will return in the 9pm slot in the first half of next year is the popular architecture programme Grand Designs.

Mr Lygo and Mr Bellamy were attempting to draw a line under what has been a turbulent year for Channel 4, during which it has faced unprecedented scrutiny and criticism over the Celebrity Big Brother racism row and its part in the call TV crisis.

He said: "A consequence of these decisions means that our ratings will most certainly fall. But then, look around - everybody's ratings are falling.

"The alternative is more of the same and that is not what Channel 4 is about. The portfolio share will remain high but the risks must then be taken by the main channel."

Although Channel 4 already does many risk-taking shows, such as Dispatches and Unreported World, Mr Lygo said it must make more.

"As others take fewer risks then by taking more we stand out from the crowd. I think Channel 4 still does take most of the risks," he added.

In a passionate speech that looked to Channel 4's past as well as its future, Mr Lygo said the broadcaster needed a strong identity and to reaffirm its public service ethos in order to help achieve a "durable financial settlement".

However, he added: "Channel 4 still has such a [public service] purpose, such a personality. It is heterodox rather than conventional.

"It is iconoclastic and individualistic rather than a scion of established values and elites. It tells the tale of ordinary voices, the deserving who are often not heard.

He added: "It is not frightened to break taboos, to expose hypocrisy and to lead campaigns. It doesn't copy others, but instead, rather prides itself on being imitated.

"It is, in a word, independent. It does nobody's bidding and is unafraid, on occasion, to court unpopularity. It always stands slightly apart, independent from government, independent from shareholders, trends, conventional wisdoms and idées fixes."

Mr Lygo also said it was time to go back to the channel's founding principle of encouraging the growth of new independent production companies, perhaps through a quota system.

He warned: "The creative naiveté of the early days has passed. We are heading, if we are not careful, for a replica of the USA: just the studios and a few massive indies."

Mr Lygo also said that the broadcaster would be reducing its annual spend on acquiring US TV shows by around £10m in 2008, with more reductions in future years.

He said the costs of US shows has "spiralled, while the return is not as great as it used to be".

US imports have have provided Channel 4 with some of its most popular and brand defining hits down the years, from Cheers to Friends and Desperate Housewives.

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